Implant, system and method using implanted passive conductors for routing electrical current

ABSTRACT

The present invention provides improvements to an implant, system and method using passive electrical conductors which route electrical current to either external or implanted electrical devices, to multiple target body tissues and to selective target body tissues. The passive electrical conductor extends from subcutaneous tissue located below either a surface cathodic electrode or a surface anodic electrode a) to a target tissue to route electrical signals from the target body tissue to devices external to the body; b) to implanted electrical devices to deliver electrical current to such devices, or c) to multiple target body tissues or to selective target body tissues to stimulate the target body tissues. The conductor has specialized ends for achieving such purposes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 11/993,393, which is the U.S. national phaseapplication of International Application No. PCT/US2006/025146, filedJun. 28, 2006, which claims the benefit of priority from U.S.Provisional Application Ser. Nos. 60/784,713, filed Mar. 21, 2006;60/703,117, filed Jul. 27, 2005; and 60/694,822, filed Jun. 28, 2005.

FIELD OF THE INVENTION

The present invention relates to improvements to an implant, system andmethod using passive electrical conductors which route electricalcurrent to either external or implanted devices, to multiple target bodytissues and to selective target body tissues.

BACKGROUND OF THE INVENTION

Electrical stimulation of body tissues and nerves is widely used forvarious indications. Several approaches are known which deliverelectrical stimulation to the targeted body area or organ. Someapproaches require focused delivery of the stimulation, while othersrequire less targeted stimulation.

Transcutaneous electrical nerve stimulation (commonly referred to asTENS) involves providing electrical signals through the skin forstimulating nerves by attaching electrodes to the skin surface. TENS isadvantageous in being non-invasive. However, its effectiveness isquestionable since the delivered stimulation is not focused and only asmall fraction of the electrical signals delivered through the skin isused effectively.

The electrodes attached to the skin surface cannot select specific bodyareas, for example particular muscles or deeper muscle tissue. TENS isgenerally limited to pain relief. However, since the stimulation can besensed by receptors in the skin, TENS can cause discomfort due tostimulation-induced pain.

Alternatively, percutaneous stimulation can be used to deliver targeted,effective stimulation without activating the skin receptors. A lead isimplanted in bodily tissues and led through the skin for connection toan external stimulator. Electrical signals are delivered through thelead to the bodily tissues. However, percutaneous stimulation is notwidely practiced since percutaneous leads are unaesthetic andunhygienic, providing a conduit for infection.

Miniature implantable stimulators, for example, the RF BION® device(Advanced Bionics Corporation, California, USA) deliver focusedstimulation, while not violating skin integrity. The implantedstimulator can be connected to an implanted lead to position thestimulator close to the skin, while delivering stimulation to deeperbody areas. The miniature implanted stimulator requires the delivery ofenergy from outside the body, which is usually accomplished by anexternal coil in proximity to the skin to generate a low-frequencymagnetic field. A disadvantage of the RF BION® device is the necessityfor an external coil. The battery-powered BION® stimulator (AdvancedBionics Corporation) avoids this problem. The BION® stimulator is aminiature implantable stimulator containing a miniature rechargeablebattery. The battery can be charged wirelessly using a charging coil,with a relatively short charging time. However, such implantablestimulators are not generally desirable due to their expense.

A system which overcomes the above problems of the current techniques isthe “router system” as described in International Publication No. WO2005/070494 A1 to Prochazka, published Aug. 4, 2005 and claimingpriority from U.S. Provisional Patent Application No. 60/538,618 filedJan. 22, 2004 (Neural Prosthesis Program Meeting, NIH Meeting, November2004; Gan et al., 2005). The router system is based on a passiveelectrical conductor (for example, a lead) which extends fromsubcutaneous tissue located below a surface cathodic electrode to thetarget body tissue. The electrical conductor has a pick-up end forallowing the electrical current to flow through the conductor, and astimulating end for delivering electrical current to the target bodytissue. A surface anodic electrode is also positioned on the skin.Advantageously, the router system applies sub-sensational levels oftranscutaneous stimulation, thereby avoiding stimulation-induced pain.Importantly, focused delivery of the stimulation to the target bodytissue is achieved via the passive electrical conductor. Due to suchsignificant advantages, further developments of the router system aredesirable.

SUMMARY OF THE INVENTION

The present invention relates to improvements to an implant, system andmethod using passive electrical conductors which route electricalcurrent to either external or implanted electrical devices, to multipletarget body tissues and to selective target body tissues.

In a broad aspect, there is provided a method for selectively andelectrically stimulating a target body tissue in a subject comprisingthe steps of:

a) providing surface cathodic and anodic electrodes for makingelectrical contact with the subject's skin;

b) providing an implant to act as a conductive pathway for at least aportion of the electrical current flowing between the surface cathodicand anodic electrodes positioned in spaced relationship on the subject'sskin and transmitting the portion of the electrical current to thetarget body tissue, the implant comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from subcutaneous tissue located below either or        both of the surface cathodic electrode or the surface anodic        electrode to the target body tissue,    -   the electrical conductor having a pick-up end and a stimulating        end, and being insulated between its ends, the pick-up end        having a plurality of conductive pick up electrodes and the        stimulating end having a plurality of conductive stimulating        electrodes, and each of the conductive pick-up electrodes being        electrically connected with one or more corresponding conductive        stimulating electrodes, such that positioning of either or both        of the surface cathodic electrode or the surface anodic        electrode over one of the conductive pick-up electrodes causes        the portion of the electrical current to be transmitted to the        one or more corresponding conductive stimulating electrodes        electrically connected to the one of the conductive pick-up        electrodes;

c) implanting the implant entirely under the subject's skin, with theconductive pick-up electrodes positioned in the subcutaneous tissue, theconductive stimulating electrodes positioned in the vicinity of thetarget body tissue, and one or more of the corresponding conductivestimulating electrodes positioned proximate to the target body tissue;

d) positioning the surface cathodic and anodic electrodes in spacedrelationship on the subject's skin, with either or both of the surfacecathodic electrode or the surface anodic electrode positioned over theconductive pick-up electrode electrically connected with the one or morecorresponding conductive stimulating electrodes which are proximate tothe target body tissue, so that the portion of the current istransmitted through the electrical conductor to the one or morecorresponding conductive stimulating electrodes for stimulation of thetarget body tissue; and

e) applying direct, pulsatile or alternating electrical current betweenthe surface cathodic electrode and the surface anodic electrode to causethe portion of the electrical current to flow through the implantsufficient to stimulate the target body tissue.

In another aspect, there is provided a system for selectively andelectrically stimulating a target body tissue in a subject, comprising:

i) surface cathodic and anodic electrodes for making electrical contactwith the subject's skin, and which, when positioned in spacedrelationship on the subject's skin, transmit electrical current tosubcutaneous tissue located below and between the surface cathodic andanodic electrodes;

ii) a stimulator external to the subject's body, electrically connectedto the surface cathodic and anodic electrodes, the stimulator supplyingelectrical current to the 15 surface cathodic and anodic electrodes; and

iii) an implant for picking up a portion of the electrical currentflowing between the surface cathodic and anodic electrodes andtransmitting the portion of the electrical current to the target bodytissue, the implant comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from subcutaneous tissue located below either or        both of the surface cathodic electrode or the surface anodic        electrode to the target body tissue, and    -   the electrical conductor having a pick-up end and a stimulating        end, and being insulated between its ends, the pick-up end        having a plurality of conductive pick-up electrodes and the        stimulating end having a plurality of conductive stimulating        electrodes, and each of the conductive pick-up electrodes being        electrically connected with one or more corresponding conductive        stimulating electrodes, such that positioning of either or both        of the surface cathodic electrode or the surface anodic        electrode over one of the conductive pick-up electrodes causes        the portion of the electrical current to be transmitted to the        one or more corresponding conductive stimulating electrodes        electrically connected with that one of the conductive pick-up        electrodes.

In another broad aspect, there is provided a method for deliveringelectrical current to one or more electrical devices implanted within asubject's body, comprising the steps of:

a) providing surface cathodic and anodic electrodes for makingelectrical contact with the subject's skin;

b) providing an implant to act as a conductive pathway for at least aportion of the electrical current flowing between surface cathodic andanodic electrodes positioned in spaced relationship on the subject'sskin and transmitting the portion of the electrical current to the oneor more electrical devices, the implant comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from the subcutaneous tissue located below        either or both of the surface cathodic electrode or the surface        anodic electrode to the one or more electrical devices,    -   the electrical conductor having a pick-up end and a delivery end        and being insulated between its ends, the pick-up end forming an        electrical termination having a sufficient surface area to allow        a sufficient portion of the electrical current to flow through        the conductor, and the delivery end forming an electrical        termination for delivering the portion of electrical current to        the one or more electrical devices;

c) providing the one or more electrical devices;

d) implanting the implant entirely under the subject's skin, with thepick-up end positioned in subcutaneous tissue located below either orboth the surface cathodic electrode or the surface anodic electrode;

e) implanting the one or more electrical devices entirely under thesubject's skin, the one or more electrical devices being positionedalong the electrical conductor or formed as the electrical terminationof the pick-up end, and the one or more electrical devices beingelectrically connected to the electrical conductor such that theelectrical current is transmitted from the electrical conductor to theone or more electrical devices;

f) positioning the surface cathodic and anodic electrodes in spacedrelationship on the subject's skin, with either or both the surfacecathodic electrode or the surface anodic electrode positioned over thepick-up end of the electrical conductor so the portion of the current istransmitted through the conductor to the one or more electrical devices,and returns to either the surface cathodic electrode or the surfaceanodic electrode through body tissues; and

g) applying direct, pulsatile or alternating electrical current betweenthe surface cathodic electrode and the surface anodic electrode to causethe portion of the electrical current to flow through the implantsufficient to deliver electrical current to the one or more electricaldevices.

In another aspect, there is provided a system for delivering electricalcurrent to one or more electrical devices implanted within a subject'sbody, comprising:

i) surface cathodic and anodic electrodes for making electrical contactwith the subject's skin, and which, when positioned in spacedrelationship on the subject's skin, transmit electrical current tosubcutaneous tissue located below and between the surface cathodic andanodic electrodes;

ii) a stimulator external to the subject's body, electrically connectedto the surface cathodic and anodic electrodes, the stimulator supplyingelectrical current to the surface cathodic and anodic electrodes;

iii) an implant for picking up a portion of the electrical currentflowing between the surface cathodic and anodic electrodes andtransmitting that portion of the electrical current to the one or moreelectrical devices, the implant comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from subcutaneous tissue located below either or        both of the surface cathodic electrode or the surface anodic        electrode to the one or more electrical devices,    -   the electrical conductor having a pick-up end and a delivery end        and being insulated between its ends, the pick-up end forming an        electrical termination having a sufficient surface area to allow        a sufficient portion of the electrical current being applied to        flow through the conductor, in preference to current flowing        through body tissue between the surface cathodic and anodic        electrodes, such that the one or more devices are supplied with        current, and the delivery end forming an electrical termination        with the one or more devices for delivering the portion of        electrical current to the one or more devices; and

iv) the one or more electrical devices being electrically connected tothe electrical conductor such that the electrical current is transmittedfrom the conductor to the one or more electrical devices.

In another broad aspect, there is provided a method for delivering anelectrical signal from a target body tissue to one or more externaldevices located external to a subject's body, the method comprising thesteps of:

a) providing a surface electrode for making electrical contact with thesubject's skin;

b) providing an implant to act as a conductive pathway for theelectrical signals from the target body tissue, the implant comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from subcutaneous tissue located below a surface        electrode positioned on the subject's skin to the target body        tissue,    -   the electrical conductor having a pick-up end and a delivery end        and being insulated between its ends, the pick-up end forming an        electrical termination having a sufficient surface area to allow        the electrical signal from the target body tissue to flow        through the conductor, and the delivery end forming an        electrical termination for delivering the electrical signal to        the one or more external devices;

c) implanting the implant entirely under the subject's skin, with thedelivery end positioned in subcutaneous tissue located below the surfaceelectrode, and the pick-up end positioned proximate to the target bodytissue; and

d) positioning the surface electrode on the subject's skin, with thesurface electrode positioned over the delivery end of the electricalconductor, the surface electrode being electrically connected to the oneor more external devices such that the electrical signal from the targetbody tissue is transmitted through the conductor to the one or moreexternal devices.

In another aspect, there is provided a system for delivering electricalsignals from a target body tissue to one or more external devices to belocated external to a subject's body comprising:

i) at least one surface electrode for making electrical contact with thesubject's skin; and

ii) an implant for picking up the electrical signal from the target bodytissue and transmitting the electrical signal to the one or moreexternal devices, the implant comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from subcutaneous tissue located below the at        least one surface electrode to the target body tissue,    -   the electrical conductor having a pick-up end and a delivery end        and being insulated between its ends, the pick-up end forming an        electrical termination having a sufficient surface area to allow        the electrical signal from the target body tissue to flow        through the conductor, and the delivery end forming an        electrical termination for delivering the electrical signal to        the one or more external devices.

In another broad aspect, there is provided a method for stimulating aplurality of target body tissues comprising the steps of:

a) providing one or more surface cathodic and anodic electrodes formaking electrical contact with the subject's body;

b) providing one or more external stimulators, the one or more externalstimulators being external to the subject's body, electrically connectedto the one or more surface cathodic and anodic electrodes, thestimulator supplying electrical current to the one or more surfacecathodic and anodic electrodes;

c) providing a plurality of implants for electrically stimulating aplurality of target body tissues independently or in unison, eachimplant acting as a conductive pathway for at least a portion of theelectrical current flowing between the one or more surface cathodic andanodic electrodes positioned in spaced relationship on the subject'sskin and transmitting the portion of the electrical current to theplurality of target body tissues, each implant comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from subcutaneous tissue located below either        the one or more surface cathodic electrodes or the one or more        surface anodic electrodes to a plurality of target body tissues,        and    -   each electrical conductor having a pick-up end and a stimulating        end and being insulated between its ends, the pick-up end        forming an electrical termination having a sufficient surface        area to allow a sufficient portion of the electrical current to        flow through the conductor such that the target body tissue is        stimulated, and the stimulating end forming an electrical        termination for delivering the portion of electrical current to        the target body tissue;

d) implanting the plurality of implants entirely under the subject'sskin, with the pick-up ends of the electrical conductors positioned insubcutaneous tissue located below either or both of the one or moresurface cathodic electrodes or the one or more surface anodicelectrodes, and the stimulating ends positioned proximate to theplurality of target body tissues;

e) positioning the surface cathodic and anodic electrodes in spacedrelationship on the subject's skin, with either or both of the surfacecathodic electrodes or the surface anodic electrodes positioned over thepick-up ends of the electrical conductors so the portion of the currentis transmitted through the conductors to the plurality of target bodytissues, so that the current flows through the plurality of target bodytissues and returns to either the surface cathodic electrodes or thesurface anodic electrodes through body tissues; and

f) applying direct, pulsatile or alternating electrical current betweenthe one or more surface cathodic electrodes and anodic electrodes tocause the portion of the electrical current to flow through theplurality of implants sufficient to stimulate the plurality of targetbody tissues.

In another aspect, there is provided a system for electricallystimulating a plurality of target body tissues in a subject comprising:

i) surface cathodic and anodic electrodes for making electrical contactwith the subject's skin, and which, when positioned in spacedrelationship on the subject's skin, transmit electrical current to theplurality of target body tissues; ii) a stimulator external to thesubject's body, electrically connected to the surface cathodic andanodic electrodes, the stimulator supplying direct, pulsatile, oralternating current to the surface cathodic and anodic electrodes; and

iii) a plurality of implants for picking up a portion of the electricalcurrent flowing between the surface cathodic and anodic electrodes andtransmitting that portion of the electrical current to the plurality ofthe target body tissues, each of the plurality of implants comprising

-   -   a passive electrical conductor of sufficient length to extend,        once implanted, from subcutaneous tissue located below either        the surface cathodic electrode or the surface anodic electrode        to the target body tissue,    -   the electrical conductor having a pick-up end and a stimulating        end and being insulated between its ends, the pick-up end        forming an electrical termination having a sufficient surface        area to allow a sufficient portion of the electrical current        being applied to flow through the conductor, in preference to        current flowing through body tissue between the surface cathodic        and anodic electrodes, such that the target body tissue is        stimulated, and the stimulating end forming an electrical        termination for delivering the portion of electrical current to        the target body tissue.

In general, the terms and phrases used herein have their art-recognizedmeaning, which can be found by reference to standard texts, journalreferences and contexts known to those skilled in the art. The followingdefinitions are provided to clarify their specific use in the context ofthe invention.

“Activating” or “activate” is meant to refer to inducing the conductionor propagation of action potentials or nerve impulses along the axons ofthe target nerve partially or completely.

“Biocompatible” means generating no significant undesirable hostresponse for the intended utility. Most preferably, biocompatiblematerials are non-toxic for the intended utility. Thus, for humanutility, biocompatible is most preferably non-toxic to humans or humantissues.

“Blocking” or “block” is meant to refer to preventing the conduction orpropagation of action potentials or nerve impulses along the axons of atarget nerve partially or completely.

“Body tissue” is meant to refer to a neural tissue (in the peripheral orcentral nervous system), a nerve, a muscle (skeletal, respiratory, orcardiac muscle) or an organ, for example, the brain, cochlea, opticnerve, heart, bladder, urethra, kidneys and 30 bones.

“Electrical device” means an device powered by electrical current orwhich processes electrical signals.

“Electrically connected” means connected in a manner to permittransmission of electrical current.

“Electrical current” is meant to refer to current applied at the surfaceof the skin that is resistively and capacitively coupled to theimplanted passive conductor, which in turn conveys the current to thetarget body tissue or device.

“Proximate” means a distance sufficiently close to stimulate the targetbody tissue including direct contact with the target body tissue.

“Stimulate” means stimulating a target nerve to either activate or blockthe conduction or propagation of action potentials or nerve impulsesalong the axons of the target nerve partially or completely.

“Subject” means an animal including a human.

“Vicinity” means a distance near the target body tissue but notsufficiently close to stimulate the target body tissue.

When a Markush group or other grouping is used herein, all individualmembers of the group and all combinations and subcombinations possibleof the group are intended to be individually included in the disclosure.Whenever a range is given in the specification, for example, atemperature range, a time range, or a composition range, allintermediate ranges and subranges, as well as all individual valuesincluded in the ranges given are intended to be included in thedisclosure.

As used herein, “comprising” is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps. As usedherein, “consisting of excludes any element, step or ingredient notspecified in the claim element. As used herein, “consisting essentiallyof does not exclude materials or steps that do not materially affect thebasis and novel characteristics of the claim. Any recitation herein ofthe term “comprising,” particularly in a description of components of acomposition or a description of elements of a device, is understood toencompass those compositions and methods consisting essentially of andconsisting of the recited components or elements. The inventionillustratively described herein suitably may be practiced in the absenceof any element or elements, limitation or limitations which is notspecifically disclosed herein.

The use of the indefinite article “a” in the claims before an elementmeans that one of the elements is specified, but does not specificallyexclude others of the elements being present, unless the context clearlyrequires that there be one and only one of the elements.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed. Thus, it should be understood that although thepresent invention has been specifically disclosed by the preferredembodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and that such modifications and variations are considered to bewithin the scope of this invention as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described by way of example onlyand with reference to the following figures in which similar referencesare used in different figures to denote similar components, and wherein:

FIG. 1 is a schematic three-dimensional view of the router system of theprior art having an implanted electrical conductor, surface cathodic andanodic electrodes, and an implanted electrical return conductor.

FIG. 2 is a schematic sectional view illustrating passive electricalconductors implanted subcutaneously for acquiring ENG signals.

FIG. 3 is a schematic sectional view illustrating passive electricalconductors implanted subcutaneously and incorporation of implantedelectrical devices with the conductors.

FIG. 4 is a schematic sectional view illustrating passive electricalconductors implanted subcutaneously and connection of implantedelectrical devices in series or in parallel with the conductors.

FIG. 5 is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously and incorporation of an ENG sensingdevice with the conductor.

FIG. 6 is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously and incorporation of anover-stimulation protection circuit with the conductor.

FIG. 7 is a schematic view illustrating waveforms for transmittingstimulus and data.

FIG. 8A is a schematic view illustrating two channels, using two surfacecathodic electrodes, two terminations and a common surface anodicelectrode.

FIG. 8B is a schematic view illustrating a single patch, two-channelssurface electrode.

FIG. 9A is a schematic view illustrating several electrical conductorsconnected to the same termination.

FIG. 9B is a schematic view illustrating several electrical conductorsconnected to terminations which are positioned under a common surfacecathodic electrode.

FIG. 10 is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously, with the conductor having a leadincorporating three conductive stimulating electrodes designated as e1,e2 and e3 and connected to three conductive pick-up electrodes p1, p2and p3, respectively

FIG. 11 is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously, and positioning of the surfacecathodic electrode over the conductive pick-up electrode p3 to divertelectrical current via the p3-e3 path.

FIG. 12A is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously, and insulation of conductive pick-upelectrodes p1 and p2 and exposure of conductive pick-up electrode p3 todivert electrical current to stimulating electrode e3.

FIG. 12B is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously, and insulation of conductive pick-upelectrode p1 and exposure of conductive pick-up electrodes p2 and p3 todivert electrical current to stimulating electrodes e2 and e3.

FIG. 12C is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously, and insulation of conductive pick-upelectrodes p2 and exposure of conductive pick-up electrodes p1 and p3 todivert electrical current to conductive pick-up electrodes e1 and e3.

FIG. 12D is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously, and positioned below both of thesurface cathodic and anodic electrodes.

FIG. 12E is a schematic sectional view illustrating two passiveelectrical conductors implanted subcutaneously, with one conductor beingpositioned below the surface cathodic electrode, and the other conductorbeing positioned below the surface anodic electrode.

FIG. 13 is a schematic view illustrating wireless selection ofconductive pick-up/stimulating electrodes by electronic circuits basedon non-volatile memory.

FIG. 14A is a schematic sectional view illustrating a passive electricalconductor implanted subcutaneously, and a branched arrangement of theconductive pick-up electrodes.

FIG. 14B is a schematic sectional view illustrating the conductivepick-up electrodes of FIG. 14A following trimming.

FIG. 15A is a schematic view illustrating a lead having a conductivepick-up electrode and three conductive stimulating electrodes.

FIG. 15B is a schematic view illustrating a lead having a conductivepick-up coil electrode with insulating backing

FIG. 15C is a schematic view illustrating a lead having a conductivepick-up circular electrode and three conductive stimulating electrodes.

FIG. 15D is a schematic view illustrating lead having a conductivepick-up circular electrode with insulating backing and three conductivestimulating electrodes.

FIG. 15E is a schematic view illustrating a lead having a conductivepick-up electrode to which insulating backing is attached duringimplantation.

FIG. 16A is a schematic plan view illustrating a “paddle type” electrodehaving a paddle with conductive stimulating electrodes and disc-shapedconductive pick-up electrodes, arranged in a line.

FIG. 16B is a schematic plan view illustrating a “paddle type” electrodehaving a paddle with conductive stimulating electrodes and disc-shapedconductive pick-up electrodes, arranged as a cluster.

FIGS. 17A and 17B are schematic sectional views illustrating aconductive pick-up electrode with insulating material implantedsubcutaneously.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention broadly relates to improvements of a “routersystem” as described in International Publication No. WO 2005/070494 A1to Prochazka (published Aug. 4, 2005 and claiming priority from U.S.Provisional Patent Application No. 60/538,618 filed Jan. 22, 2004), andU.S. patent application Ser. No. 11/337,824 filed Jan. 23, 2006 to Gauntand Prochazka. These applications describe an implant for electricallystimulating a target body tissue, such as a nerve, in a subject toeither activate or block neural impulses depending on the condition tobe treated.

FIG. 1 taken from WO 2005/070494 A1 shows the subject's skin 10, a nerve12, nerve sheath 14, and a muscle 16. The implant 18 provides aconductive pathway for at least a portion of the electrical currentflowing between the surface cathodic and anodic electrodes 20, 22. Theimplant 18 comprises a passive electrical conductor 24 of sufficientlength to extend, once implanted, from subcutaneous tissue located belowthe surface cathodic electrode 20 to the target body tissue 12. Theelectrical conductor has a pick-up end 26 and a stimulating end 28, ofwhich one or both form electrical terminations having sufficient surfaceareas for reducing the electrical impedance of the interface between thepick-up and stimulating ends 26, 28 of the electrical conductor 24 andthe surrounding body tissues. The terminations 30 are shown in FIG. 1 inthe form of an embracing cuff 32 placed around the nerve 12. An optionalelectrical return conductor 34 provides a low-impedance conductivepathway from the target body tissue to the surface anodic electrode 22,thereby concentrating the electric field through the target tissue 12.The electrical return conductor 34 has a collecting end 36 and areturning end 38. Cathodic wire 42 and anodic wire 44 are connected toan external stimulator (not shown) to which operating power is providedby a power source (not shown). Once implanted, the implant 18 provides aconductive pathway for at least a portion of the electrical currentflowing between the surface cathodic and anodic electrodes 20, 22.

The router system has been described in International Publication No. WO2005/070494 A1 and U.S. patent application Ser. No. 11/337,824 asbeneficial for various conditions in which stimulation to eitheractivate or block neural impulses is required. Such conditions caninclude movement disorders (e.g., spasticity, hypertonus, rigidity,tremor and/or muscle weakness, Parkinson's disease, dystonia, cerebralpalsy), muscular disorders (e.g., muscular dystrophy), incontinence(e.g., urinary bladder disorders), urinary retention, pain (e.g.,migraine headaches, neck and back pain, pain resulting from othermedical conditions), epilepsy (e.g., generalized and partial seizuredisorder), cerebrovascular disorders (e.g., strokes, aneurysms), sleepdisorders (e.g., sleep apnea), autonomic disorders (e.g.,gastrointestinal disorders, cardiovascular disorders), disorders ofvision, hearing and balance, and neuropsychiatric disorders (e.g.,depression). The router system may also be used for promoting bonegrowth (as required, for example, in the healing of a fracture), woundhealing or tissue regeneration.

The present invention contemplates use of the router system for specificcategories of conditions described in Table 1:

TABLE 1 Summary of Conditions Category of Condition Examples of SpecificConditions Functional/ Hand rehabilitation, gait control, transfers andstanding, FES-induced Rehabilitation bicycling, arm cranking, FESsystems for grasping and reaching, ejaculation, erectile dysfunction,dysphagia, cervical dystonia, diaphragm pacing, fecal incontinence,cough assistance, improvement of circulation, prevention and treatmentof pressure sores, prevention or treatment of osteoporosis. Thetermination (stimulating electrode) is positioned near the appropriatemotor point. For example, for treatment of foot drop, the stimulatingelectrode may be located near the common peroneal nerve. The pick-up endis positioned on the leg, below the knee. The external stimulusgenerator delivers the required stimulation (for example, symmetric orasymmetric stimulation, 30 pulses per second, 200 μsec pulse width) upontriggering by a Foot Sensor, indicating heel on/heel off events.Exercise Shoulder subluxation, cerebral palsy, Bell's palsy.(Spasticity/Pain The termination (stimulating electrode) is positionednear the Prevention) appropriate motor point. For example, for treatmentof shoulder subluxation, the stimulating electrode may be positionednear the axillary nerve. The pick-up end is positioned below the skin inthe shoulder area. The external stimulator is activated for a specifictime, for example 1 hour, with symmetric or asymmetric stimulation, 30pulses per second, 200 μsec pulse width, 5 sec ON and 5 sec OFF time.Orthopedic Prevention/reversal of muscle atrophy, knee replacement (postRecovery procedure pain) Pain treatment can be delivered in severalways, namely by stimulating subcutaneously, stimulating peripheralnerves, or stimulating nerve roots, for example in the epidural space.Pain treatment stimulation usually requires higher frequencies (morepulses per second) as compared to the motor point stimulation—usuallywithin the range of 30-50 pulses per second. The termination(stimulating end) is positioned in the appropriate area, and the pick-upend is positioned subcutaneously in a convenient space. An optimallocation is one that does not cause the lead to cross the joints, or thepick-up end to be positioned in the moving area. The stimulation isinitiated or stopped by the patient. Systemic pain Cancer pain, terminalillness pain, rheumatoid arthritis, osteoarthritis, phantom limbsyndrome, bursitis, causalgia, multiple sclerosis, postherpeticneuralgia (shingles), synovitis, diabetic peripheral neuropathy,neuralgia. For these purposes, the router system is applied in a similarmanner as described for the orthopedic recovery applications. Head andneck Cluster headaches, dental disorders, migraine headaches,spondylosis, pain sprains, strains, suboccipital headaches, TMJdisorders, torticollis, whiplash, thoracic outlet syndrome. For thesepurposes, the router system is applied in a similar manner as describedfor the orthopedic recovery applications. Abdominal pain Diverticulosis,dysmenorrhea, labor pain, Caesarean section (post- operative pain),incisions (post-operative pain). For these purposes, the router systemis applied in a similar manner as described for the orthopedic recoveryapplications. Back pain Facet syndrome, intercostal neuralgia,sacroiliac joint dysfunction, lumbago, lumbosacral pain, radiculitis,IVD syndrome, degenerative disc disease, spinal stenosis, sprains,strains, throacodynia, whole back pain. For these purposes, the routersystem is applied in a similar manner as described for the orthopedicrecovery applications. Extremity pain Sprains, strains, fractures,ischialgia, tendonitis, peripheral nerve injury, subdeltoid bursitis,frozen shoulder, impingement syndrome, epicondylitis, elbow pains,lateral epicondylitis, medical epicondylitis, radial tunnel syndrome,cubital tunnel syndrome, wrist pain, DeQuervain's tenosynovitis, Guyon'scanal syndrome, hand pain, trigger finger and thumb, intersectionsyndrome, sciatica, knee pain, ankle pain, foot pain, stretch pain,thrombophlebitis, Raynaud's syndrome, Carpal Tunnel Syndrome. For thesepurposes, the router system is applied in a similar manner as describedfor the orthopedic recovery applications. Cosmetic Electrical musclestimulation to supplement regular training to fully exhaust muscle andto speed up recuperation to enhance maximum strength, maintain musclesat peak condition when normal exercise is suspended due to injury, toneup slack muscles, maintenance of peripheral circulation, relax musclesin case of strain, firm loose abdominal muscles to regain shape afterchildbirth. For these purposes, the router system is applied in asimilar manner as described for the functional/rehabilitationapplications.

The categories of conditions in Table 1 broadly relate to musclestimulation (e.g., functional/rehabilitation stimulation, prevention ofpain or spasticity, orthopedic recovery); pain treatment; and cosmeticapplications. Functional/rehabilitation stimulation attempts to restorenormal activity by activating selected muscles.Functional/rehabilitation stimulation can be continuous (e.g., asapplied to urge incontinence) or repeatable (e.g., as applied todiaphragm-pacing, arm rehabilitation and gait control). Prevention ofpain or spasticity includes stimulation applications for preventingpain, rather than suppressing pain. Orthopedic recovery includes musclestimulation to prevent atrophy or prevention of post-procedure pain asassociated with knee replacement. The same areas of the body may bestimulated; for example, radiculitis and lower back pain may overlap andhave the same stimulation sites. Cosmetic applications includeelectrical stimulation targeted at cosmetic improvements, for example,electrical stimulation to help build and maintain muscles in peakcondition (e.g., when normal exercise is suspended due to injury),maintain peripheral circulation, relax muscles following strain, or firmabdominal muscles following childbirth.

The present invention contemplates that the router system can be used todeliver electrical current to either external or implanted devices, tomultiple target body tissues and to selective target body tissues asdescribed below.

A. Delivery of Electrical Energy to External and Implanted ElectricalDevices Using the Router System

The present invention contemplates that the router system can be used todeliver electrical energy to one or more electrical devices which arepowered by electrical current or which process electrical signals.Non-limiting examples of such electrical devices may include, forexample, sensors (for example, ENG sensors, temperature sensors,pressure sensors, pH sensors, impedance sensors, and others known to oneskilled in the art), amplifiers, filters, high voltage/constant currentgenerators, switches, power supplies, batteries, battery-chargingcircuits, miniature rechargeable batteries, processors, frequencyshifters, over-stimulation protection circuit, communication modules(wired or wireless) and other suitable devices known to those skilled inthe art. Such electrical devices can be either external to the body orimplanted within the body.

Implanted electrical devices are preferably biocompatible and non-toxic,or enclosed in a biocompatible case, generating no significantundesirable host response for the intended utility. For example,biocompatible sensors for assessing intra-body parameters andpre-processing circuits, communication circuits and power supplycircuits are typically implanted within the body, such that raw datafrom implanted electrical devices, for example sensors, are transmittedto devices external to the body, for example, post-processing circuitswhich involve sophisticated algorithms, and greater processing power,space and power requirements compared to implanted devices.

i) Use of Router System with External Electrical Devices

The router system can be used to deliver electrical signals (monopolarand bi-polar signals) from target tissues within the body(electroneurographic or ENG signals) to external electrical devices. Asan example, ENG is a common non-invasive test for examining theintegrity of target tissues or organs by recording the spontaneouselectrical activity of target tissues or organs, or by assessing theresponse of electrically excitable tissues or organs to stimulation. Asa further example, the Auditory Brainstem Response (ABR) test providesobjective information about the upper auditory system including theinner ear and brainstem. The target tissue is typically a nerve, forexample a peripheral nerve, or organ for example a particular muscleinnervated by a nerve.

FIG. 2 illustrates use of the router system for acquiring ENG signals.Two surface electrodes (for example, two surface cathodic electrodes 20a and 20 b) are shown positioned separately over two implanted passiveelectrical conductors 24 a and 24 b. Electrical conductor 24 a isfocused in proximity to first point of the nerve 12, while electricalconductor 24 b is in proximity to a second point of the same nerve 12.One surface reference electrode (for example, surface anodic electrode22) is positioned on the skin 10.

Electrical conductors 24 a and 24 b deliver the electrical signal fromthe first and second points of the nerve 12, respectively. Adifferential amplifier 46 is provided to amplify the difference betweenthe ENG signals at each of the first and second points of the nerve 12.Measurement of the amplified electrical signal is subsequently performedfor example, by an RMS meter, peak meter, or oscilloscope, or digitaldata acquisition system. Differential amplifier 46 a amplifies thesignal at the first point (ENG1), while differential amplifier 46 bamplifies the signal at the second point (ENG2). Alternatively, the ENGsignal can be amplified by a differential amplifier connected between anelectrical conductor 24 and a surface reference electrode (for example,surface anodic electrode 22).

The signal-to-noise ratio of the ENG signal can be improved byimplanting an amplifier. The amplifier is implanted and connectedbetween the conductors 24 a and 24 b. The amplifier amplifies the ENGsignal and delivers the amplified signal via the electrical conductor 24and termination 30 to an external signal acquisition device which isconnected between the external surface electrodes 20 a and 20 b. Theimplanted amplifier and additional electronic circuits (for example, aseries of amplifiers; a band pass filter to limit the bandwidth to onlythe signals of interest; or a band stop filter to prevent entry of 50 Hzor 60 Hz induced by the power lines) can be powered by an externalgenerator delivering sub-threshold current through the skin 10.

Various conditions require use of the router system as described aboveto deliver electrical signals from target tissues within the body; forexample, monitoring of gastric activity. Deviations in the electricalpattern of gastric activity can be indicative of different pathologicalconditions, for example, delayed gastric emptying time. The prior artapproach is to record electrical activity by external electrodes, whichhave the disadvantage of being exposed to electrical noise andelectrical signals from non-targeted organs. The present applicationcontemplates that the router system as useful in the stomach area toimprove the ability to monitor these signals.

ii) Use of Router System with Implanted Electrical Devices

The present invention contemplates that the router system can be alsoused to deliver electrical current to one or more implanted electricaldevices 48. For this purpose, the implanted passive electrical conductor24 has a pick-up end 26 and a delivery end 28 (rather than a stimulatingend 28 per se). The pick-up end 26 allows a sufficient portion ofelectrical current to flow through the electrical conductor 24. Thedelivery end 28 delivers electrical current to one or more electricaldevices 48.

Further, the present invention contemplates that the router system canbe used for dual purposes, namely to deliver electrical current to oneor more implanted devices 48, and to stimulate a target body tissue. Forthis purpose, the implanted passive electrical conductor 24 has one endwhich is a pick-up end 26 and another end which acts as both a deliveryend 28 to deliver electrical current to one or more implanted electricaldevices 48, and a stimulating end 28 to deliver electrical current to atarget body tissue.

For illustrative purposes, the electrical conductor 24 is schematicallyshown in FIGS. 3, 4, 5 and 6 as being positioned under the surfacecathodic electrode 20; however, it will be appreciated by those skilledin the art that the electrical conductor 24 can be positioned beloweither or both of the surface cathodic electrode 20 or the surfaceanodic electrode 22.

Implanted electrical devices 48 can be positioned anywhere along theelectrical conductor 24 or can be formed as part of the termination 30for example, of the pick-up end 26. FIG. 3 illustrates severalapproaches as examples for incorporating implanted electrical devices 48with the router system. An external stimulator 50 delivers sub-threshold(or above threshold) transcutaneous electrical current picked up by atermination 30 a, 30 b, 30 c. Implanted devices 48 can be built as partof the termination 30 a (for example, device 48 a); as separate butadjacent to the termination 30 b (for example, device 48 b); or asseparate and remote relative to the termination 30 c (e.g., implantednear the nerve as for example, device 48 c).

As shown in FIG. 4, the implanted electrical device 48 can be connectedin series, as illustrated by the positioning of device 48 a. Theexternal stimulator 50 provides electrical current to the surfacecathodic electrode 20 which is delivered to termination 30 a. Theelectrical current picked up by termination 30 a (designated as “It”)then flows through device 48 a, continues through the electricalconductor 24 a and the stimulating end 28 a to be delivered into thetarget body tissue, for example nerve 12. The electrical current returnsthrough the body tissue and the surface anodic electrode 22 to theexternal stimulator 50. Alternatively, a “parallel” connection, asillustrated by the positioning of device 48 b, can be used. The device48 b consumes a portion (designated as “le”) of the “It” electricalcurrent picked up by the termination 30 b. The return current is shownflowing from device 48 b through body tissue to the surface anodicelectrode 22. The electrical current (designated as “Is” which is It-le)flows via the electrical conductor 24 b to the stimulating end 28 b andreturns to the surface anodic electrode 22 through body tissue.

Various conditions require use of the router system as described aboveto deliver electrical signals to implanted devices within the body. Forexample, implanted amplifiers can improve the quality of the acquisitionof the intra-body electrical signals. Electrical current is delivered topower the amplifier. The required current can be, for example, less than1 mA, and at a frequency of higher than 50 KHz in order to pass easilythrough the skin, to avoid sensation or stimulation, or to avoidinterference with the measured ENG signal.

As an example, FIG. 5 illustrates the use of the router system todeliver electrical energy to implanted devices for acquiring ENG signalsfrom a target tissue, for example a nerve 12. The implanted devicesshown generally at 48 include a power supply 52, a differentialamplifier 46, a frequency shifter 54 and a reference electrode 56. Thereference electrode 56 serves to measure the difference of potentialsbetween it and the nerve 12, as picked by the stimulating end 28 and areference electrode located elsewhere in the tissue. The referenceelectrode 56 can be positioned within the distance of severalmillimeters to several centimeters of the stimulating end 28. Theexternal stimulator 50 delivers a sub-threshold signal, which can be,for example, a sinusoidal signal having a frequency outside those of theENG, to the surface cathodic electrode 20 which delivers the electricalcurrent to termination 30. The electrical current, picked up bytermination 30, is then rectified and stabilized by the power supply 52.In order to deliver energy through the tissue without causing skinirritation, pain, or local muscle contractions, the external stimulator50 is used to deliver a symmetrical waveform of high frequency, forexample, usually higher than 30-50 KHz. In order to power the electroniccircuitry, and specifically the differential amplifier 46, DC current isrequired. Power supply 52 rectifies the current delivered by thestimulator 50 to pick-up electrode 30, and than stabilizes it andcreates the required voltages/currents. The power supply 52 in turndelivers power to the differential amplifier 46. The differentialamplifier 46 amplifies the nerve signal 12 picked up by the stimulatingend 28. The amplified signal is then fed back to the termination 30 tothe external cathodic electrode.

Specifically, the current flows from the external stimulator 50 to thesurface cathodic electrode 20, via capacitive coupling to termination30, via power supply 52 to electronic circuits, e.g. amplifier 46,continues to the electrical conductor 24, stimulating end 28, andreturns through the tissue to the surface anodic electrode 22, to theexternal stimulator 50. It will be appreciated by those skilled in theart that the signals generated by the amplifier 46 and the frequencyshifter 54 can be superimposed on the same current path. These signalsdo not interfere with the measurements, since a frequency shifter 54 canbe optionally provided to shift the amplified ENG signal outside thefrequency spectrum of the original ENG signal, thereby preventinginterference with the original ENG signal. Several techniques are knownin the art to achieve frequency shifting, for example, amplitudemodulation (where the signal is mixed with a carrier wave, resulting inshifting the original signal spectrum to be around the carrierfrequency), single side band modulation (SSB), frequency modulation (FM)and phase modulation (PM). The signal can be transmitted in its analogform or using digital encoding. The amplified signal can be processed byusing analog or digital processing techniques; for example, theamplified signal can be filtered by an external filter 58, shifted backto the original frequency, and output for the further processing.

As is known to those skilled in the art, time division could be used. Inone time slot, the ENG signal is amplified and recorded in the implantedmodule or recording device, and in the next time slot, the recordedsignal is transmitted through the termination 30. Wireless transmissionof the information also can be applicable.

As a further example, FIG. 6 illustrates use of the router system todeliver electrical energy to an over-stimulation protection circuitshown generally at 60. A controller 62 and a power supply 52 areimplanted in connection with the passive electrical conductor 24. Thecontroller 62 includes a switch 64 for selectively disconnecting thestimulating end 28. The disconnection can be performed, for example, ifthe electrical current exceeds a pre-defined threshold. Alternatively,an external device can be used to provide a signal to connect ordisconnect the stimulating end 28. The power supply 52 can incorporate anon-volatile memory to store a serial number or code number of anexternal stimulator 50. The external stimulator 50 transmits a numberand, if the number matches the stored number, the stimulating end 28 isthen connected; otherwise, the stimulating end 28 is disconnected. Thisapproach prevents use of unauthorized or unapproved externalstimulators.

As yet a further example, the router system can be used to deliverelectrical energy to charge implanted batteries. For example, miniatureimplantable stimulators can be charged using this approach.

One of the possibilities for transmitting both stimulus and data isshown in FIG. 7. One possible approach is to transmit the data betweenthe successive stimuli. The data is transmitted, for example, bymodulating a sub-threshold sine wave. Amplitude modulation is shown inthe example; however, various other modulation techniques alternativelycould be used.

B. Stimulation of Multiple Target Body Tissues Using the Router System

International Publication No. WO 2005/070494 A1 and U.S. patentapplication Ser. No. 11/337,824 describe an embodiment of the routersystem as involving a plurality of implants for electrically stimulatingmore than one target body tissue independently or in unison to activateneural impulses. The presence of multiple implants necessitatespositioning of a plurality of surface cathodic electrodes, and one ormore surface anodic electrodes appropriately relative to the implants tostimulate the different target body tissues independently or in unison.One or more external stimulators are required. The present inventioncontemplates several arrangements as set out below.

For illustrative purposes, the electrical conductor 24 is schematicallyshown in FIGS. 8A, 9A and 9B as being positioned under the surfacecathodic electrode 20; however, it will be appreciated by those skilledin the art that the electrical conductor 24 can be positioned beloweither or both of the surface cathodic electrode 20 or the surfaceanodic electrode 22.

a) A Plurality of Surface Cathodic Electrodes 20 Sharing One SurfaceAnodic Electrode 22, and One or More External Stimulators 50 can beUsed.

In this arrangement, each surface cathodic electrode 20 a, 20 b ispositioned over a separate implanted passive electrical conductor 24 a,24 b which extends to a different target body tissue 12 a, 12 b. Eachelectrical conductor 24 a, 24 b forms an electrical termination 30 a, 30b at its pick-up end 26 a, 26 b, and provides a conductive pathway forat least a portion of the electrical current flowing between theplurality of surface cathodic electrodes 20 a, 20 b and the one anodicelectrode 22. Each surface cathodic electrode 20 a, 20 b can beconnected either to separate stimulators 50 a, 50 b (Le., creating twoseparate channels as shown in FIG. 8A) or to a single multi-channelstimulator 50 (for example, a single patch, two-channels surfaceelectrode arranged on conductive material 65 as shown in FIG. 8B). Thesurface anodic electrode 22 can be connected to each of the separatestimulators 50 a, 50 b or to the single multi-channel stimulator 50.

b) One Surface Cathodic Electrode 20 and One Surface Anodic Electrode 22Sharing One External Stimulator 50 can be Used.

In this arrangement, the surface cathodic electrode 20 is positionedover one termination 30 to which more than one separate implantedpassive electrical conductors 24 a, 24 b, 24 c are connected by anysuitable means, for example, a crimp connection 67 or by welding (FIG.9A). In an alternate arrangement, the surface cathodic electrode 20 canbe positioned over more than one separate termination 30 a, 30 b inorder to provide electrical current to more than one electricalconductor 24 a, 24 b (FIG. 9B).

c) A Segmented Surface Cathodic Electrode

In order to compensate for a possible misalignment of the surfacecathodic electrode 20 and the stimulation, the surface cathodicelectrode 20 can be divided into segments, with each segment beingconnected individually to an external stimulator 50 by a switchingmatrix. The switches are operated either manually or by a controller.Electrical stimulation is thereby delivered mainly to the area of thesurface cathodic electrode 20 which is positioned above the termination30 of the electrical conductor 24. It will be appreciated by one skilledin the art that appropriate algorithms can be determined to deliveroptimal stimulation; for example, by choosing the segment having thelowest impedance. This arrangement provides easier alignment with theelectrical conductor 24; a smaller skin surface 10 conducting theelectrical current; and a way of balancing stimulation when a pluralityof electrical conductors 24 are present.

The situation might arise where the stimulation site, for example theback, might not be easily accessible. A solution is to implant thetermination 30 in an accessible place, and to tunnel a lead to thetarget body tissue. The stimulation site can be either focused (i.e.,adjacent the target body tissue) or dispersed (i.e., not adjacent to anyspecific target body tissue).

The above arrangements require one or more external stimulators 50 forsupplying electrical current to the surface cathodic and anodicelectrodes 20, 22.

Suitable external stimulators 50 include an external stimulator 50connected to electrodes 20, 22, a portable stimulator 50 attached toelectrodes 20, 22 and including a power source, or a portable stimulator50 controlled by a remote control.

The external stimulator 50 can be simply connected by the cathodic andanodic wires 42, 44 to the surface cathodic and anodic electrodes 20, 22placed on the skin 10 (as shown in FIG. 1). However, attachment of theelectrodes 20, 22 might be challenging, requiring individual placementof the electrode 20, 22 and individual connection of the electrode 20,22 to the stimulator 50. The inconvenience may be extreme on unreachablebody parts, e.g., on the shoulder. Further, the size of the stimulator50 might limit mobility of the subject. While acceptable forapplications requiring limited duration of stimulation, it might belimiting for other applications.

Alternatively, a portable stimulator 50 which includes cathodic andanodic electrodes 20, 22 and display and control buttons can be used.However, access to the stimulator's control and display buttons might beinconvenient and/or limited. For example, placement on the shoulder willprevent access to such display and control buttons. The portablestimulator 50 includes, but is not limited to, multiple-use electrodes,a limited user interface (on/off LED) and remote control unit withdisplay and control functions. However, this set-up requires anadditional device in the form of the remote control, and additionalregulatory aspects (for example, FCC, European Radio regulations). Asingle remote unit can be used to control several stimulators 50 whichmight require more complicated communication protocol and unique ID foreach stimulator 50 in order to prevent collision between differentusers.

The difficulty of positioning surface cathodic and anodic electrodes 20,22, for example on the shoulder, can be overcome by using a flexiblegarment or a rigid orthosis. Non-limiting examples include the T-CUFF™(A. Prochazka, University of Alberta) comprising a glove in which thestimulator is embedded, and the NESS H200™ (NESS Ltd., Israel)comprising a rigid orthosis having embedded electrodes and a stimulatorconnected by a wire.

Various conditions require use of the router system as described aboveto deliver electrical signals to multiple target body tissues; forexample, arm rehabilitation generally requires alternative operation offlexors and extensors. The pick-up electrodes 20 for activating flexorsand extensors can be positioned under the skin 10 in the forearm. Theactivation may be achieved, for example, by applying pulses of 200 μsecduration, 30 pulses per second, for several seconds, alternating betweenflexors and extensors.

C. Use of the Router System to Stimulate Body Tissues Selectively

Although the router system can be used to stimulate multiple target bodytissues as discussed above, greater stimulation of particular bodytissues over others may be needed. For example, in subcutaneousstimulation for pain treatment, it may be required to stimulate theentire area of pain. The present invention further contemplates that therouter system can be used to deliver electrical current selectively.

The passive electrical conductor 24 can be formed from a lead 66 havinga pick-up end 26 and a stimulating end 28 (for example, as shown in FIG.10). The pick-up end 26 can comprise one or more conductive pick-upelectrodes 68, and the stimulating end 28 can comprise one or moreconductive stimulating electrodes 70. The conductive stimulatingelectrode 70 on the lead 66 usually has a optimal size. If theconductive stimulating electrode 70 is too small, for example, havingsurface of less than 10 mm², the transfer impedance between theconductive stimulating electrode 70 and the target body tissue 12 willbe too high. If the conductive stimulating electrode 70 is too large,for example, greater than 50-60 mm², the current density delivered bythe conductive stimulating electrode 70 will be too low to activatetarget body tissue, for example the nerve 12. The optimal length of theconductive stimulating electrode 70 is usually of several millimeters,preferably 3-4 mm, having an area of about 20 mm². It is generallypositioned in the vicinity of the targeted nerve, preferably 1-3 mm,more preferably 1 mm or less. Due to constraints of implantation andconcern of mechanical nerve damage, the conductive stimulating electrode70 is generally not placed touching the nerve; otherwise, the requiredstimulation levels will be too high, causing undesirable sensationsand/or local muscle contractions.

Since such accuracy in insertion of the lead 66 is challenging, asolution is to implant an array of electrodes 68, 70 and to activate theelectrodes 68, 70 in the desired locations, or to implant a combinationof electrodes 68, 70 resulting in an optimal delivery of stimulation,known as “current steering.” The ability to select different pick up orstimulating electrodes 68, 70 during or after implantation of the lead66 can be beneficial; for example, if the stimulating end 28 or thetarget tissue have migrated within the body and the selected stimulatingelectrode 70 is no longer in the vicinity of the target body tissue; orif any wires between the pick-up electrode 68 and the stimulatingelectrode 70 become damaged.

FIG. 10 (panel A) shows an implanted passive electrical conductor 24comprising a lead 66 incorporating three conductive stimulatingelectrodes 70 designated as e1, e2 and e3 and three conductive pick-upelectrodes 68 designated as p1, p2 and p3, respectively. FIG. 10 (panelB) shows that each conductive pick-up electrode 68 has a correspondingconductive stimulating electrode 70. Alternatively, each conductivepick-up electrode 68 can have more than one corresponding conductivestimulating electrode 70. Conductive stimulating electrode e3 ispositioned closest to the target body tissue (i.e., nerve 12). A surfacecathodic electrode 20 is positioned on the skin 10 above the conductivepick-up electrode “p1.” The electrical current provided to the surfacecathodic electrode 20 flows through “p1” and “e1” to the surface anodicelectrode 22 (e1 is the corresponding conductive stimulating electrodefor conductive pick-up electrode p1). Most of the electrical current isthus not delivered to the nerve 12. However, as shown in FIG. 11,positioning the surface cathodic electrode 20 over the conductivepick-up electrode p3 diverts the current via the p3-e3 path, resultingin the electrical current passing in the vicinity of the nerve 12 toprovide stimulation (e3 is the corresponding conductive stimulatingelectrode for conductive pick-up electrode p3).

To simplify the positioning of the surface cathodic electrode 20 overthe conductive pick-up electrodes 68, the surface cathodic electrode 20can be sized to overlap one or more conductive pick-up electrodes 68,although delivery of the electrical current might be less focused.Further, one or more conductive pick-up electrodes 68 can be exposed,while the remaining conductive pick-up electrodes 68 are insulated witha layer of single use or removable and re-attachable electricalinsulation. The insulation layer can be scratched, cut or dissolvedduring the fitting process (i.e., testing which conductive pick-up andstimulating electrodes 68, 70 are the most efficient to deliverstimulation to the target body tissue). Alternatively, the insulationlayer can be removed and re-attached to the conductive pick-up electrode68 by suitable means, for example a sleeve which is either slidable overthe conductive pick-up electrode 68 to provide insulation preventing theflow of electrical current, or removable and re-attachable to expose theconductive pick-up electrode 68, thereby receiving the flow ofelectrical current.

FIG. 12A illustrates conductive pick-up electrodes p1 and p2 which areinsulated and conductive pick-up electrode p3 which is exposed. Theelectrical current is subsequently diverted to the conductivestimulating electrode e3 positioned in the vicinity of the nerve 12 (e3is the corresponding conductive stimulating electrode for conductivepick-up electrode p3). FIG. 12B illustrates the nerve 12 positionedbetween conductive stimulating electrodes e2 and e3. Insulation ofconductive pick-up electrode p1 and exposure of conductive pick-upelectrodes p2 and p3 diverts electrical current to conductivestimulating electrodes e2 and e3, thereby stimulating the nerve 12.

In a further aspect, FIG. 12C illustrates two nerves 12 a, 12 b, withconductive stimulating electrode e3 positioned at one nerve 12 a andconductive stimulating electrode e1 positioned at the other nerve 12 b.Conductive pick-up end p2 is insulated, while conductive pick-upelectrodes p1 and p3 are exposed. Electrical current is diverted toconductive pick-up electrodes p1 and p3, which deliver the electricalcurrent to conductive pick-up electrodes e1 and e3 respectively, tostimulate the nerves 12 a, 12 b.

For illustrative purposes, the electrical conductor 24 is schematicallyshown in FIGS. 10, 11, 12A, 12B and 12C as being positioned under thesurface cathodic electrode 20; however, it will be appreciated by thoseskilled in the art that the electrical conductor 24 can be positionedbelow either or both of the surface cathodic electrode 20 or the surfaceanodic electrode 22. For example, FIG. 12D illustrates an implantedpassive electrical conductor 24 having a lead 66 incorporating threeconductive pick-up electrodes 68 designated as p1, p2 and p3 and threeconductive stimulating electrodes 70 designated as e1, e2 and e3,respectively. The conductive pick-up electrodes 68 of the lead 66 arepositioned below both the surface cathodic and anodic electrodes 20, 22Conductive pick-up electrode p1 is positioned below the surface cathodicelectrode 20, and conductive pick-up electrode p3 is positioned belowthe surface anodic electrode 22 (e1 is the corresponding conductivestimulating electrode for conductive pick-up electrode p1, while e3 isthe corresponding conductive stimulating electrode for conductivepick-up electrode p3).

FIG. 12E illustrates two implanted passive electrical conductors 24 a,24 b. Electrical conductor 24 a has a lead 66 a incorporating threeconductive pick-up electrodes 68 a designated as p1, p2 and p3, andthree conductive stimulating electrodes 70 a designated as e1, e2 ande3, respectively. Electrical conductor 24 a is positioned below thesurface cathodic electrode 20, with conductive pick-up electrode p3located below surface cathodic electrode 20 (e3 is the correspondingconductive stimulating electrode for conductive pick-up electrode p3).Electrical conductor 24 b has a lead 66 b incorporating two conductivepick-up electrodes 68 b designated as p4 and p5, and two conductivestimulating electrodes 70 b designated as e4 and e5, respectively.Electrical conductor 24 b is positioned below the surface anodicelectrode 22, with conductive pick-up electrode p4 located below thesurface anodic electrode 22 (e4 is the corresponding conductivestimulating electrode for conductive pick-up electrode p4).

In yet a further aspect, wireless or wired selection of conductivepick-up and stimulating electrodes 68, 70 can be achieved by including,for example, electronic circuits based on non-volatile memory 72 (FIG.13). The electrical current is picked by the conductive pick-upelectrodes (p1, p2, p3, p4) and passes through an implanted power supply52 to operate the non-volatile memory 72. Outputs of the non-volatilememory 72 drive switches (T1, T2, T3, T4) which enable or disable thepath of electrical current between the conductive pick-up electrodes(p1, p2, p3, p4) and the conductive stimulating electrodes (e1, e2, e3,e4). A pre-defined pattern picked by the conductive pick-up electrodes68 activates a programming circuit 74 to change the non-volatile memory72 so that different patterns of the conductive stimulating electrodes70 can be selected.

Alternatively, a switching matrix based on shape memory alloy (SMA) canbe used. SMA is a metal which remembers its geometry. After a sample ofSMA has been deformed from its original conformation, it regains itsoriginal geometry by itself during heating when exposed to a temperatureabove a particular threshold. By heating the SMA contact, it changes itsshape and disconnects the stimulating electrode. For example, SMAchanges its shape when heated to 5° C. above the body temperature, andit will maintain this new shape unless it will be cooled 5° C. below thebody temperature.

Transcutaneous heating performed for example, by an ultrasonic beam, canoperate the SMA based switch from ON to OFF. Non-limiting examples ofSMA include copper-zinc-aluminum, copper-aluminum-nickel, andnickel-titanium alloys.

Testing of conductive pick-up and stimulating electrodes 68, 70 can beconducted, for example during implantation. Following implantation ofthe conductive stimulating electrodes 70 at the target body tissue, theconductive pick-up electrodes 68 still protrude percutaneously. Theconductive pick-up electrodes 68 can be connected directly to theexternal stimulator 50, and the best conductive pick-up electrode 68 maybe chosen. The external stimulator 50 is connected (e.g. with a clamp)to a certain conductive pick-up electrode or a combination ofelectrodes. The response is observed. For example, in the case of motorpoint stimulation, the combination which causes the lowest activationthreshold may be selected. As a further example, in the case of paintreatment, the patient response is examined. If the stimulation causes atingling sensation and the pain disappears, it is an indication ofsuccessful combination of the electrodes.

One method of selecting pick-up electrodes 68 is to position the surfaceelectrode (for example, surface cathodic electrode 20) over a particularimplanted pick-up electrode (for example, pick-up electrode p3 as shownin FIG. 14A). Alternatively, electrodes which are not used may betrimmed during the implantation and fitting procedure (FIG. 14B).

Non-limiting examples of leads 66 useful for the described “currentsteering” and other applications described herein are illustrated inFIGS. 15A-15E. FIG. 15A shows a lead 66 having a conductive pick-upelectrode 68 and three conductive stimulating electrodes 70. Insulatingbacking 76 can be attached to the conductive pick up electrode 68 toincrease efficacy of the pick-up end 26. Suitable insulating backing 76can include, for example, silicone, polyester fiber such as Dacron™(lnvista, Inc) or other appropriate biocompatible materials. FIG. 15Billustrates a lead 66 having a conductive pick-up coil electrode 68 withinsulating backing 76. FIG. 15C shows a lead 66 having a conductivepick-up circular electrode 68 and three conductive stimulatingelectrodes 70, with FIG. 15D showing a conductive pick-up circularelectrode 68 with insulating backing 76 and three conductive stimulatingelectrodes 70. FIG. 15E shows a lead 66 having a conductive pick-upelectrode 68 to which also insulating backing 76 can be attached, forexample, during implantation.

A further non-limiting example of a lead 66 is a double helix leadenclosed in a sheath. The construction of the double helix, the anchorand other parts is similar to the lead described by Memberg et al.(1994). Memberg et al. (1994) describe a lead including a double helixenclosed in a sheath. The double helix is separated and thenon-insulated wires are wound back on the stimulating end to which ananchor is attached. Similarly, an electrode without an anchor may serveas a single pick-up end electrode. For the purposes of the presentinvention, the lead of Memberg et al. (1994) has been modified. At thepick-up end 26, the double helix is separated and the wires wound back,forming two separate conductive pick-up electrodes 68. Similarly, at thestimulating end 28, the double helix is separated and the wires arewound back, forming two separate conductive stimulating electrodes 70.Alternatively, the double helix is separated and the wires are woundback separately to form two separate conductive pick-up electrodes 68and two separate conductive stimulating electrodes 70. Optionally,anchor-shaped tines can be formed at the stimulating end 28 to anchorthe conductive stimulating electrodes 70 in position.

Alternatively, commercially available multiple electrodes leads 66 canbe connected via matching connectors to the array of conductive pick-upelectrodes 68. Non-limiting examples include Axxess 3/6 lead (AdvancedNeuromodulation Systems Inc., USA) or TO type lead (Dr. Osypka, GmbHMedizintechnik, Germany).

An implant including a plurality of conductive stimulating electrodes 70arranged as a cluster on a non-conductive substrate, a lead 66, and aplurality of conductive pick up electrodes 68 arranged either in a lineor as a cluster can be used. For example, FIGS. 16A and 16B show a“paddle type” electrode 78 incorporating both conductive pick-up andstimulating electrodes 68, 70. FIG. 16A illustrates a “paddle type”electrode 78 having a paddle 80 with conductive stimulating electrodes70, and disc-shaped conductive pick-up electrodes 68 arranged in a line.FIG. 16B illustrates a “paddle type” electrode 78 having disc-shapedconductive pick up electrodes 68 arranged as a cluster. The advantagesof specific arrangement depends on the size and the shape of the areathat should be covered by the electrodes.

Optionally, a conductive pick-up electrode 68 with insulating material82 covering its surface and periphery is beneficial. Electrical currentfrom the surface cathodic electrode 20 may “escape” (escaping currentdesignated as “lescape”) from the periphery of the conductive pick-upelectrode 68 into the tissue (FIG. 17A). The path of this electricalcurrent through the skin 10 may be short (indicated as “d”); thus, theresistance of the path may be small. It is known that the larger thediameter of the conductive pick-up electrode 68, the larger theperipheral area. This phenomenon acts against and may neutralizeimproved transcutaneous delivery for the larger diameter of theconductive pick-up electrode 68. In order to attenuate “lescape,”insulating material 82 is can be applied to cover the periphery of theconductive pick-up electrode 68 to cover the distance similar to thethickness of the skin 10 (FIG. 17B). Alternatively, insulating material82 can be positioned below and extended beyond the conductive pick-upelectrode 68. Suitable insulating material 82 can include, for example,silicone, polyester fiber such as Dacron™ (Invista, Inc) or otherappropriate biocompatible materials. In this arrangement, the surfacecathodic electrode 20 is preferably at least 10 mm in diameter. Theconductive pick-up electrode 68 is preferably at least 16 mm indiameter. The conductive pick-up electrode 68 is covered with forexample, at least 3 mm of insulating material 82 on its periphery.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionincludes all such variations and modifications. The invention alsoincludes all of the steps, features, compositions and compounds referredto or indicated in this specification, individually or collectively, andany and all combinations of any two or more of said steps or features.

All references cited in the present application are incorporated intheir entirety by reference to the extent not inconsistent herewith.

REFERENCES

-   Gan, L., Bornes, T., Denington, A. and Prochazka, A. (2005) The    stimulus router: a novel means of directing current from surface    electrodes to nerves. IFESS 2005 Conference Proceedings, pp. 21-23.-   Memberg W. D., Peckham P. H, Keith M. W. (June 1994) A surgically    implanted intramuscular electrode for an implantable neuromuscular    stimulation system. IEEE Transactions on Rehabilitation Engineering    2(2): 80-91.-   Prochazka, A. (2004) Neural Prosthesis Program Meeting, NIH Meeting,    November 2004.

PATENT DOCUMENTS

-   Gaunt, R. A. and Prochazka, A. Method of routing electrical current    to bodily tissues via implanted passive conductors. U.S. patent    application Ser. No. 11/337,824, filed Jan. 23, 2006.-   Prochazka, A., Wieler, M., Kenwell, Z. R., Gauthier, M. J. A. (1996)    Garment for applying controlled electrical stimulation to restore    motor function. U.S. Pat. No. 5,562,707, issued Oct. 8, 1996.-   Prochazka, A. Method and apparatus for controlling a device or    process with vibrations generated by tooth clicks. International    Patent Application Publication No. WO 2004/034937, published Oct.    16, 2003.-   Prochazka, A. Method of routing electrical current to bodily tissues    via implanted passive conductors. International Publication No. WO    2005/070494 A1, published Aug. 4, 2005.-   Prochazka, A. Method and apparatus for controlling a device or    process with vibrations generated by tooth clicks. U.S. Pat. No.    6,961,623, issued Nov. 1, 2005.

1. An apparatus, comprising: a passive electrical conductor having afirst end portion and a second end portion, the first end portionincluding a stimulation electrode, the second end portion including apick-up electrode, the passive electrical conductor configured to bedisposed within a body such that the stimulation electrode is disposedadjacent a target tissue and the pick-up electrode is entirely beneath asurface of a skin; and an insulation member coupled to the second endportion of the passive electrical conductor, the insulation memberconfigured to define, at least in part, a current pathway within thebody along which a portion of an electrical current flows between asurface electrode coupled to the surface of the skin and the pick-upelectrode.
 2. The apparatus of claim 1, wherein the passive electricalconductor is insulated between the first end portion and the second endportion.
 3. The apparatus of claim 1, wherein the insulation member isconstructed from any one of silicone and polyester.
 4. The apparatus ofclaim 1, wherein the insulation member is configured to inhibit the flowof the electrical current through a portion of a subcutaneous tissue. 5.The apparatus of claim 1, wherein at least a portion of the insulationmember is disposed between the pick-up electrode and the stimulationelectrode.
 6. The apparatus of claim 1, wherein at least a portion ofthe insulation member is disposed about a periphery of the pick-upelectrode.
 7. The apparatus of claim 1, wherein: the pick-up electrodeis a first pick-up electrode from a plurality of pick-up electrodes; andthe insulation member is configured to be movably coupled to the passiveelectrical conductor such that the insulation member can selectivelycover a second pick-up electrode from the plurality of pick-upelectrodes.
 8. The apparatus of claim 1, wherein at least a portion ofthe pick-up electrode has a coil shape.
 9. The apparatus of claim 1,wherein the stimulation electrode is a stimulation electrode from aplurality of stimulation electrodes.
 10. The apparatus of claim 1,wherein a surface area of the stimulation electrode is less thanapproximately 50 square millimeters.
 11. The apparatus of claim 1,wherein a surface area of the stimulation electrode is betweenapproximately 10 square millimeters and approximately 50 squaremillimeters.
 12. The apparatus of claim 1, wherein: the pick-upelectrode is a pick-up electrode from a plurality of pick-up electrodes;and the stimulation electrode is a stimulation electrode from aplurality of stimulation electrodes, each stimulation electrode from theplurality of stimulation electrodes being electronically coupled to acorresponding pick-up electrode from the plurality of pick-upelectrodes.
 13. The apparatus of claim 1, further comprising: an anchorcoupled to the first end portion of the passive electrical conductor,the anchor configured to limit movement of the stimulation electroderelative to the target tissue when the passive electrical conductor isdisposed within the body.
 14. A method, comprising: inserting aconductive member within a body such that a stimulating electrodedisposed at a distal end portion of the conductive member is adjacent atarget tissue within the body and a pick-up electrode disposed at aproximal end portion of the conductive member is beneath a surface of askin of the body; and moving at least a portion of an insulation memberrelative to the proximal end portion of the conductive member after theinserting.
 15. The method of claim 14, wherein an exterior surface ofthe conductive member is insulated between the distal end portion andthe proximal end portion.
 16. The method of claim 14, wherein the movingincludes sliding the portion of the insulation member about the pick-upelectrode.
 17. The method of claim 14, wherein the moving includesdefining at least a portion of a current pathway within the body betweenthe surface of the skin and the pick-up electrode.
 18. The method ofclaim 14, wherein the moving includes positioning at least the portionof the insulation member between the pick-up electrode the stimulationelectrode.
 19. The method of claim 14, further comprising: coupling asurface electrode to the surface of the skin such that at least aportion of the pick-up electrode is below the surface electrode.
 20. Themethod of claim 14, wherein the insulation member is coupled to theproximal end portion of the conductive member before the inserting.